Resonators in fluid conduits for avoiding unpleasant acoustic emissions when the fluid vibrates in the fluid conduit have been known and used for a long time. At the present time, they are mostly constructed from plastics, use being made predominantly of injection moldings but also of blow moldings. Injection moldings have the disadvantage that the resonators have a plurality of individual parts and therefore require a fairly complicated assembly or welding process. Blow molding, on the other hand, is a relatively inexpensive production method and therefore the use of blow moldings is increasingly targeted.
DE 10 2008 016 690 A1 shows a resonator of the type in question in which both resonator parts are configured as blow moldings. The parts each have a collar and are connected to one another airtight at the collars.
The technical teaching disclosed here allows only resonators with just one resonance chamber. This single chamber is connected to the actual fluid conduit via an annular gap (19). Although this solution is distinguished by great simplicity, its range of use is only limited since multi-chamber systems cannot be achieved without further effort.
U.S. Pat. No. 5,806,480 discloses a fluid conduit which has, in a longitudinal section, two nested tubes, between which a chamber surrounding the inner tube is arranged. In this case, the chamber communicates via openings machined into the inner tube with the interior of the inner tube. To produce this tubular piece, the inner tube is first of all injection molded. A blank for the outer tube is then produced via an extrusion process and is bent in such a way that it surrounds the inner tube. The outer tube blank is then reshaped via a blow molding process in order to produce the outer tube.
The process for bending, blow molding and fastening the outer tube on the inner tube is quite complex and a tool of complicated construction is required since the entire bent conduit section must be inserted into the tool (see FIG. 3 of U.S. Pat. No. 5,806,480), and therefore a separate tool has to be provided for each conduit section and since the blow molding step is not very precisely defined as regards the maintenance of the shape of the inner part, despite the connecting openings.